cushion foam

Memory Foam Outdoor Cushions: An Honest Answer on Whether They Work

Memory foam feels great in a bed but struggles outside: it changes with temperature, soaks up water and dries slowly. Here's how it compares with reticulated and high-density foams, what density and IFD mean, and what we use instead.

By Sam K7 min read
Three foam blocks on a sunlit outdoor table: dense white foam, open-cell reticulated foam and memory foam with a handprint, with water droplets

Memory foam is lovely in a bed and a poor choice for a patio chair. That's why we don't sell memory foam at Fabrica Kraft, even though customers often ask about it. Here's what happens to it outside, and what we put in outdoor and indoor cushions instead.

Quick answer

Memory foam is not a good choice for outdoor cushions. It gets firmer in cold weather and softer in heat, and it soaks up rain and dries slowly, which can lead to mold inside the cushion. Use reticulated quick-dry foam such as Dryfast outdoors, and high-density foam with a soft wrap indoors for a similar sink-in feel.

What is memory foam?

Memory foam is a type of polyurethane foam that sinks slowly under your weight and comes back slowly when you get up. The technical name is viscoelastic foam. "Visco" means it flows like thick honey, and "elastic" means it springs back in the end.

It started in the air. According to NASA's Spinoff publication, engineer Charles Yost created the open-cell "memory" foam in 1966 under a NASA contract, to make airplane seats safer and more comfortable.

The Polyurethane Foam Association (PFA), the US foam industry's trade group, says this foam is known for its slow recovery after it's pressed down. That slow, molding feel is the whole point in a mattress. On a deck, it causes problems.

Why doesn't memory foam work well outdoors?

Memory foam reacts to temperature, water and sun, and outdoor cushions get all three. Indoors, your thermostat and roof protect it. Outside, nothing does.

It changes with the weather

The PFA says memory foam's "memory" action works best between about 55°F and 85°F. It also says warmth makes the foam recover faster.

Below that range, the foam stiffens. A memory foam seat can feel noticeably harder on a cool spring morning than it did the afternoon before. In strong sun on a dark cover, it goes the other way: soft, slow and saggy.

It holds water

Memory foam is open-cell, but it's dense and the cells are small. The PFA says household memory foam usually weighs 2 to 6 pounds per cubic foot. Water gets in easily and leaves slowly.

Mattress makers say the same in their care guides. Puffy, for example, warns that memory foam pillows absorb water easily and must be dried fully to prevent mold. It also says not to wring them, because the foam can tear.

Sun wears it down

Most flexible cushion foam, memory foam included, is a polyether polyurethane. The reference book PUR Facts notes that polyether foams are more sensitive to oxidation and damage from light than polyester types. In plain terms, foam that gets sun through a thin fabric tends to yellow, crumble and lose its bounce over time.

Can memory foam get wet?

Memory foam can get wet without being ruined right away. The real risk is how long it stays wet. A soaked cushion that sits in damp shade can start growing mold deep inside, where you won't see it until you smell it.

The EPA's guide to mold says the key to mold control is moisture control. It advises drying wet items within 24 to 48 hours to prevent mold growth. Thick memory foam after a summer storm often won't dry that fast.

How does memory foam compare with other cushion foams?

Here's how memory foam stacks up against the three foams we use most. The notes on our foams are simple, plain-English descriptions, not lab numbers.

Foam Water Temperature Feel Best use Outdoors?
Memory foam Soaks up water and dries slowly Firmer in cold, softer in heat Slow sink, slow rebound Mattresses, pillows, indoor toppers Not recommended
Dryfast (reticulated) Water drains straight through No slow "memory" effect Springy, slightly coarse Patios, pools, boats Yes, our first choice
HD36-R (high density) Absorbs water, so keep it dry No slow "memory" effect Supportive, all-purpose Indoor seats, benches, window seats Covered areas only, kept dry
Lux-R (luxury) Absorbs water, so keep it dry No slow "memory" effect Firm, long-lasting Sofa and lounge seats you sit on daily Covered areas only, kept dry

What do foam density and IFD mean?

Density tells you how long a foam will last. IFD tells you how firm it feels. They are two different things.

Density is how much a cubic foot of foam weighs, measured in pounds per cubic foot. The PFA says that as density goes up, foam usually loses less firmness over time. So denser foam tends to hold its shape longer.

IFD stands for indentation force deflection, and some sellers call it ILD (indentation load deflection). The PFA defines it as the pounds of force needed to press a foam sample down by 25% of its height. A higher number means a firmer foam.

The PFA also points out that firmness and density are independent. A dense foam can feel soft, and a lighter foam can feel firm. Our guide to the right foam grade for an outdoor cushion goes deeper on this.

What foam should you use for outdoor cushions?

For cushions that live outside, use reticulated foam. We use Dryfast. Reticulated foam is foam with the thin skins between its cells removed, leaving an open, net-like frame.

Foam maker FXI describes reticulation as removing the cell membranes so only the struts are left. With those skins gone, water runs straight through Dryfast instead of soaking in. Air moves through too, so the cushion dries fast after rain or a hosing down.

We recommend Dryfast for uncovered patio sets, pool loungers and boats, held in place with ties. It carries a 5-year foam warranty. It feels a little springier than dense indoor foam.

How do you get a soft, sink-in seat without memory foam?

Use a high-density foam core and wrap it in Dacron. That gives you a soft top layer and a seat that springs back right away. Most people asking for custom memory foam cushions really want this feel.

  • HD36-R: high-density, all-purpose foam with a supportive feel. A good pick for dining benches and window seats. 7-year foam warranty.
  • Lux-R: our luxury grade, firm and built to last, at around 1.8 pounds per cubic foot. 7-year foam warranty.
  • Dacron wrap: a layer of polyester batting around the foam. It softens the top, rounds the edges and fills out the cover.
  • Super Soft: very soft and comfortable, but for back cushions only. It's too soft to hold up under a seat, so we never use it for one.

Every foam we sell is CertiPUR-US certified. According to CertiPUR-US, certified foam is made without ozone depleters, formaldehyde and CPSC-regulated phthalates, and is tested for low indoor emissions of under 0.5 parts per million. You can compare our grades side by side in the custom foam collection.

How do you replace the foam in an outdoor cushion?

Measure the old cushion, pick the right foam, and order it cut to size. If your covers are still in good shape, it's an easy weekend job.

  1. Unzip the cover and take out the old foam.
  2. Measure width, depth and thickness. Measure the cover, not the flattened old foam.
  3. Note the shape: rectangle, trapezoid, round or a custom curve.
  4. Choose your foam: Dryfast for outdoor use, HD36-R or Lux-R for indoor or covered seats.
  5. Order custom-cut foam inserts to your measurements and slide them into the covers.

Not sure about thickness? Read how thick a seat cushion should be first. Our builder makes 3 to 5 inches as standard, up to 8 inches, and custom shapes made from your paper template take 5 to 6 weeks.

Frequently asked questions

Is memory foam good for outdoor cushions?

No, not for most outdoor seating. Memory foam gets firmer in the cold and softer in the heat. It also soaks up rain and dries slowly, which raises the risk of mold inside the cushion.

Can memory foam get wet?

It can, but it absorbs water easily and dries slowly. The EPA advises drying wet items within 24 to 48 hours to prevent mold. If memory foam gets soaked, press the water out gently, don't wring it, and dry it fully in a shady, airy spot.

What is the best foam for outdoor cushions?

Reticulated foam, such as our Dryfast, is the best choice for cushions that get rained on. Its open, net-like structure lets water drain straight through. Air flows through it too, so it dries quickly.

Does Fabrica Kraft make custom memory foam cushions?

No, we don't sell memory foam. For a soft, sink-in seat indoors, we use HD36-R or Lux-R with a Dacron wrap. For outdoor cushions, we use Dryfast.

Is Dryfast foam waterproof?

No, and that's the point. Dryfast doesn't keep water out. It lets water pass straight through so the foam doesn't stay wet.

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